As employed herein, the terms "local" and "regional" with respect to anesthesia are intended to be synonymous and interchangeable.
When a surgeon operates on the legs or arms, local anesthesia may be performed as continuous regional anesthesia. In continuous regional anesthesia, by using an epidural needle, a catheter is then introduced through the needle, with the front, distal end of the catheter projecting out of the needle to lie beside the nerves. Typically, in order to determine correct positioning of the needle, a small, test dose of anesthesia is administered through the needle, followed by inserting the catheter through the needle. Selected catheters have an integral conductive wire through which an electrical current may be applied to determine correct positioning after the catheter has been inserted through the needle. Then, the needle is removed and the catheter is left in place so that more local anesthetic drugs can be administered through the catheter.
Various attempts have been made to improve on anesthesia instruments.
For instance, U.S. Pat. No. 5,119,832 to Xavier shows an epidural catheter that includes four (4) circumferential ring electrodes, each connected to conductive wires embedded in the wall of the catheter. Thus, anesthetics or narcotics can be administered through the catheter, in conjunction with providing electrical stimulation through the electrodes in order to control pain.
Additionally, of interest is U.S. Pat. No. 5,378,241 to Haindl, which shows an epidural cannula with a TUOHY-type beveled aperture such that the cannula has a sufficiently large diameter so that both an epidural catheter and a spinal cannula can be simultaneously positioned inside of the epidural cannula.
In another variation, a guide wire is first inserted through a spinal cannula that is inside of an epidural cannula, followed by removing the spinal cannula and then inserting a spinal catheter over the path of the guide wire and within the epidural cannula, as disclosed in U.S. Pat. No. 4,994,036 to Biscoping et al.
Various other anesthesia instruments of interest are disclosed in U.S. Pat. No. 4,518,383 to Evans; U.S. Pat. No. 4,775,367 to Schmidt; U.S. Pat. No. 4,889,529 to Haindl; U.S. Pat. No. 4,917,670 to Hurley et al.; U.S. Pat. No. 4,917,668 to Haindl; U.S. Pat. No. 5,085,631 to Leighton; U.S. Pat. No. 5,106,376 to Mononen et al.; U.S. Pat. No. 5,135,525 to Biscoping et al.; U.S. Pat. No. 5,312,374 to Gurmarnik; U.S. Pat. No. 5,328,479 to Gurmarnik; U.S. Pat. No. 5,512,052 to Jesch; and U.S. Pat. No. 5,630,802 to Moellmann et al.
The disclosures of all patents mentioned are incorporated herein by reference.